The invention relates to an apparatus making it possible to continuously treat compounds in a corrosive liquid and more particularly intended for dissolving nuclear fuels in boiling nitric acid during the reprocessing of said fuels.
During the different reprocessing stages of nuclear fuels, it is known that the rods containing said field are generally sheared into sections before being immersed in a boiling nitric acid bath which serves to separate the fuel from the mechanical parts. Thus, the nuclear fuel is dissolved in nitric acid, whilst the can fragments and the other metal parts are not dissolved.
Among the different known apparatuses making it possible to dissolve nuclear fuels in nitric acid an apparatus is known in which the acid is placed in a fixed tank, the can fragments being successively introduced into the buckets of a bucket wheel which rotates so as to immerse the fragments in acid, after which the fragments and other undissolved parts are removed in order to discharge them out of the apparatus. In this known apparatus, the bucket wheel is driven and supported by a shaft which traverses the tank walls and which is rotated by a motor positioned outside the vessel. The axial guidance of the bucket wheel is by means of a system of rails and rollers positioned between the tank and outer periphery of the wheel.
This known apparatus has a number of disadvantages mainly resulting from the corrosive nature of the hot nitric acid used.
One of the disadvantages is due to the rotation of the wheel by a shaft passing through the vessel walls level with the wheel axle, i.e. in a part of the vessel positioned just above the level of the acid. During the dissolving of the nuclear fuels in the nitric acid bubbling takes place on the surface level thereof leading to a spattering of the boiling acid above the level occupied by the acid at rest. This spattering of acid leads very rapidly to the damaging of the rotary gaskets necessary for the tightly sealed passage of the wheel drive shaft.
Another disadvantage of this known apparatus also due to the corrosive nature of the boiling nitric acid, is the arrangement of a certain number of wheel guide rollers directly in the acid. This leads to the risk of these rollers being very rapidly damaged to the extent that they are no longer usable. This latter disadvantage is made worse by the fact that it is not possible to dismantle and replace the rollers in the aforementioned apparatus.